1. Technical Field
The present invention relates to a carton blank for forming a carton, and a carton which is to be filled with a consumable product accessible through an opening in the carton. More particularly, the invention pertains to an opening feature formed in a top panel of the carton which provides a reliable and a consistent opening when opened by the consumer.
2. Background Art
Paperboard cartons have been manufactured with a variety of opening features which allow the consumer access to the contents of the cartons. These features may consist of perforations, herringbone cuts, adhesive weaknesses, as well as other means of providing a point along the top panel, side panel or hinge lines where the carton may be most readily opened. A further opening feature commonly employed in cartons of this type is that of double-cut scores, as shown in U.S. Pat. No. 3,399,820 to Foster et al.
The above-mentioned opening feature is formed by way of double-cut scores; i.e., an inner and outer cut in the paperboard which run parallel to one another. By so providing these cut score lines, when the consumer applies an upward force or opening force on the pull tab provided between the pairs of cut score lines, ply separation occurs in the regions between the inner and outer cut score lines. Continued pulling of the pull tab causes complete separation of the opening flap to allow the consumer unobstructed access to the contents of the carton.
Similar opening features are disclosed in U.S. Pat. No. 4,746,109 to Prater and U.S. Pat. No. 4,613,046 to Kuchenbecker. As in the above-mentioned patent, a line of weakness is provided in a panel of a respective carton where ply separation of the panel is permitted to occur when the consumer applies an opening force to the pull tab. The ply separation occurs between two pairs of reverse cut lines which are formed at least halfway through the panel of the carton. However, when forming the paperboard blanks which are to be later used in erecting the cartons disclosed, it is extremely difficult to accurately achieve the desired extent of the cut lines in both the top and bottom cut. These paperboard blanks are formed in a matrix which consists of a plurality of forming dies and counters. Because the paperboard must be cut on both sides thereof to form the double or reverse cuts, an extensive alignment procedure must be undertaken to assure that each cut formed in each side of each paperboard blank of the matrix is properly formed.
U.S. Pat. No. 4,687,104 to Ielmini discloses a similar carton and carton blank having score lines formed in the outer and inner surfaces of the top and the front flap. These score lines are referred to as extending partially through the outer and inner surfaces of the carton and carton blank. Given this assertion, the carton formed by the reverse score lines of U.S. Pat. No. 4,687,104 is no more reliable than the cartons set forth above. These cartons, as explained above, are difficult to manufacture due to variations in the depths of the die cut score lines which are experienced during their formation and which are difficult to control. Consequently, the resulting carton will not open as prescribed.
U.S. Pat. No. 2,974,852 issued to Huss et al. discloses a top panel opening feature which includes a continuous perforation line which is encircled by a cut score line. This allows the encircled portion of the top panel to be completely removed from the carton thus permitting access to the contents of the carton. The top panel is pressed downwardly in order to randomly rupture the line of weakness about the opening portion and, consequently, the ply separation of the top panel of the carton may not reliably occur in a specified area; and, moreover, the ply separation may, in fact, never commence resulting in tears in the top panel.
In an attempt to overcome the shortcomings associated with the foregoing prior art, U.S. Pat. No. 4,951,824 issued to Kuchenbecker et al., the disclosure of which is hereby incorporated herein by reference, discloses a carton having a reliable opening feature for use in containers wherein it is imperative that the carton remain impervious to moisture or other environmental effects. The opening feature includes an uncut line of weakness extending substantially parallel to a partially cut line of weakness with each of the lines of weakness being formed from the same side of the carton blank. However, the ply separation is initiated at the fold line of the front flap which may result in a misdirection of the ply separation.
As can be seen from the foregoing, there is clearly a pressing need for a carton of the above-mentioned type which will provide a reliable, and consistent opening feature that is capable of being opened with ease by the consumer, and which will not retard the structural integrity of the carton when opened.